1. Field of the Invention
The present invention relates to an audio reproducing apparatus for reproducing data from, for example, a disc recording medium.
2. Description of the Related Art
It is known in the art that a reproducing-only apparatus or recording/reproducing apparatus on which a magneto-optical disc or an optical disc is operated for audio reproduction is required to operate on as small an electric power as possible for a longer playback time. This requirement is especially conspicuous with a portable, compact apparatus with its power supplied from an internally installed battery such as a dry battery or a rechargeable battery.
Meanwhile, U.S. Pat. No. 5,214,631 (Maeda, et al.) for example discloses a reproducing apparatus for reproducing data from a magneto-optical disc or an optical disc (such as a compact disc) wherein the data read from a recording medium through an optical head is temporarily stored in a buffer memory unit from which it is read at a predetermined timing to be converted into a reproduced audio signal.
In the above-mentioned constitution, a bit transfer rate at which the data read through the optical head is sent to the buffer memory is set to a higher level than a rate at which the data is read from the buffer memory. Consequently, the data is written to the buffer memory at a higher rate than it is read from the buffer memory, so that the buffer memory always holds a certain amount of data read through the optical head when the data is always read from the buffer memory. This allows to put out a reproduced audio signal without interruption even when the optical head is temporarily disabled by a track jump or the like caused by an external disturbance for example.
In the above-mentioned reproducing apparatus, the operation of the optical head and the operation of a signal system between the optical head and the buffer memory are performed intermittently so that the data is not supplied to the buffer memory in excess of an available write space in the buffer memory even when the data is written at a high transfer rate. While the data is not supplied to the buffer memory, the optical head is kept in a pause state. In the pause state, the optical head repeats a one-track jump operation to scan a same track until the amount of data in the buffer memory drops blow a predetermined level.
The duration of time in which the optical head is kept in the pause state, or a standby state, depends on a size of the buffer memory and settings of read/write transfer rates. For example, if a 74-minute magneto-optical disc is reproduced on an apparatus in which data is written to the buffer memory at a rate about five times as fast as it is read from it, the writing operation takes only one fifth of an actual overall reproducing time, or about 14 to 17 minutes in this example, keeping the optical head in the standby state in the remaining four fifths of the time. In other words, the optical head keeps repeating the one-track jump operation for the four fifths of the total reproducing time, wasting an electric power of the apparatus for a long time.